Nighttime pollination under threat from light pollution

New study suggests that artificial light may disrupt the fragile network of plants and pollinators.

Light pollution may be negatively impacting nocturnal pollinators and the plant communities that depend on them.
(Photo: Justin Kern/Flickr)

The increasing glow from artificial lights around the world is ruining our night skies, messing with our trees, and according to a new study, possibly disrupting critical pollination networks.

Writing in the journal Nature, a group of scientists from Switzerland has identified light pollution as a previously unknown threat to nocturnal insects (beetles, moths and flies) vital in the pollination of crops and wild plants. To study its impact on nighttime communities, the team deployed standard LED street lights over plots of cabbage thistle in the remote meadows of the Bernese Prealps.

"As it is possible that light sensitive insects have already disappeared in regions with high levels of light pollution, we conducted our study in the still relatively dark Prealps," team leader Eva Knop's from the Institute of Ecology and Evolution at the University of Bern said in a statement.

An example of one of the artificial light tests setup in a mountain meadow in Switzerland. (Photo: UniBE/Maurin Hörler)

Before the lights were switched on, the researchers used night vision goggles to record the nighttime visits of more than 300 different species of insects to the meadow's flowers. With the artificial lights engaged, insect visits dropped more than 62 percent. Of the 100 cabbage thistle plants that Knop's team investigated, the half exposed to the artificial light produced 13 percent fewer fruits that their unlit counterparts.

"Even though daytime pollinators are usually more numerous than night-time pollinators, they were unable to make up the difference in lost pollination of plants kept under artificial lighting. This [could] be because some studies have shown that night-time pollinators seem to be more effective at transferring pollen between plants than their diurnal counterparts," Knop wrote in the study. "Thus, it is not just the quantity but also the quality that counts."

According to the researchers, the study is the first of its kind to show how light pollution not only impacts nocturnal pollinators, but also the ability of plants to make seeds. The stresses this may place on diurnal populations further complicates the global pollinator crisis.

"Urgent measures must be taken, to reduce the negative consequences of the annually increasing light emissions on the environment," urged Knop.

For some perspective on the various levels of light pollution pollinators must contend with throughout throughout the U.S., check out the video below.